Niall Horan and Hailee Steinfeld ignited dating rumors during President's Day Weekend when they attended a Backstreet Boys concert together on Saturday night. Their BSB moment was caught by a fan ninergrl6, who hit up Twitter to share videos of the pair dancing, singing along and joking around with each other to the sounds of the boy band in the Axis Theater's VIP section at Planet Hollywood Resort and Casino in Las Vegas.

In the videos, both Hailee and Niall can be seen getting down to the Boys' hit song "I Want It That Way." At one point, A.J. McLean even comes up to the One Direction member and sings with him!

For the possible date night in Sin City, Hailee opted for a plunging black top and jeans. The Brit donned a laidback plaid shirt and jeans.

A source confirms to E! News that after the concert the duo hit up at XS Nightclub where they sat together at a stage table with a few friends, sipping on Absolut Elyx cocktails and taking in a DJ set by Diplo.

This isn't the first time that the two have hung out together. The "Starving" singer and the "Slow Hands" crooner were previously photographed together at the 2017 American Music Awards at Microsoft Theater on November 19, 2017 in Los Angeles.

Niall had already set the rumor mill spinning in December after he shared a sweet birthday tribute to the Edge of 17 actress on Instagram and wrote, "Happy birthday to the loveliest person on the planet and one of my best friends @haileesteinfeld. Have no idea what the hell is going on in this photo. Love ya hails."

Fans online were quick to speculate that Saturday's night out on the town meant that the self-admitted best friends were more than just friends, with many commenting that something is going on with the stars.

Meanwhile Hailee was believed to be dating social media personality Cameron Smoller, whom she's been linked to since 2016. The couple has not announced a split, but do not currently follow each other on social media. Hailee has not appeared on Cameron's Instagram since Nov. 15, 2017.

Additionally, in the February issue of Marie Claire Hailee did talk about love and heartbreak, saying, "I’m trying to protect myself and have a bit of a guard up, but I also want to fall in love and know why love hurts."